For the mixing of a gas with a liquid there are used, for example, perforated nozzles through the perforations of which the gas is directed under pressure into the liquid.
FIG. 5 in publication GB-1115288 also shows a mixing apparatus in which a liquid and a gas are fed tangentially into a space between two cylindrical surfaces, the liquid into the upper section and the gas into a lower point, under an annular skirt. The mixture is withdrawn upwards via a connection in the center. In this apparatus, the cross-sectional area of the opening which leads out of the annular mixing space is greater than the area of the feed connections.